In a photovoltaic module (panel) the panel is made up of series-connected mono crystalline or polycrystalline solar cells, each having a forward voltage of around 0.6V, that is a forward diode drop. These are then series connected to form sub-strings, nominally of around 10V for a 60 cell module, and 12V for a 72 cell module. Under certain circumstances the solar PV modules can become partly shaded, for example from fallen leafs or from part of a building and no longer generate current or voltage. It is desirable to be able to improve the power harvest from a PV panel under such circumstances, in particular whilst protecting the PV panel from damage.
Background prior art can be found in: WO2010/144637; U.S. Pat. No. 7,031,176; JP2006-041440; EP2286645A; and US 2009/0080226.